tdi issues....1998 jetta

[shegel]

this is what my dad posted on tdi club but no one has been able to help yet. anyone have any input

I have a 98 jetta tdi and I have had it for a year. I bought the car from a guy who didn't want to have the intake cleaned again after only 20k since it was cleaned before.
Bought the car and had the local shop clean the intake and install new fuel filter. I have had to advance the timing 3 times due to hard start problems. Replaced the tb and it will start eventually if I pump the pedal(engine hot or cold). when cold idles at 1000 for about a minute or so then it will rev up. I have very little power untill about 2200 rpm.
runs worse with maf disconnected.
did the cage mod on all electrical connections-no change
removed the fuel tank to check it (clean)and blew out the lines from the pump back. no change
bypassed filter and thermostatic tee and bled lines,no change.
replaced all vacum lines-no change
installed lift pump-no change.
bought a vag com and checked timing, in upper range, fuel temp 143, timing 62
cleaned intake and intercooler myself-no change
turbo spins freely
egr mod check -idling at 903rpm value at 32768 displays shows 850 mg/stroke and 450 mg/stroke which is way off what what FAQ section says it should be ( 250 mg/stroke)

I am at a lost. I have the vag com but not sure what to check, how to check it or what to do next.
Only thing I can think of is that maybe the head itself is clogged by the valves but I dont really want to pull the head just to check it.
Any help would be appreciated

[Quantum TD]

Mileage would help, along with a detailed history of how it ran, then what happened after repairs, etc.

Having said that, has he checked out the glow system? Even with a bad plug or two, the car would start up but perhaps run like doo. It's a quick check, and doesn't cost a dime to do. THe procedure is outlined in TDIclub under TDI 101 FAQ.

Next, disconnect the temperature sensor on the engine (also covered in the GLow-Plugs 101 in TDIClub). If the car starts right up and runs fine with the sensor disconnected, then the temp sensor is bad.

Next, I'd check the N75 if he has't checked that yet. You can test it with an ohmeter. I'm not sure of the value for the resistance, but on the 1.8t, it's like 35 ohms. If resitance is infinite, or zero, then the N75 valve is bad. They go bad frequently, and it controls the boost to the turbo electronically.

You can also test it manually. Disconnect the vacuum hose to the wastegate, connect a hand-vacuum pump to the wastegate, and pump up the pressure as high as it will go. Then start the car. If it runs fine, then you know that your N75 is not creating vaccum to keep the waste-gate open and it should be replaced. If the hand-vacuum pump does not register any vacuum at all when applied to the wastegate, then your wastegate is bad, and needs to be replaced.

When he had the intercooler hoses off, id he check for breaks/splits, etc. That will cause you to lose boost.

Who did the timing belt? Did he do it, or a sketchy shop. Perhaps the injection pump is off a tooth. It can happen given the amount of play in the lock pin on the 1998 TDI.

If all of the above check out and do not solve your problem, then I'd say that you have a mechanical problem. Have the injectors pop-tested. If they check out, then look to the injection pump. So long as the shop did not drop crud into the intake ports when they cleaned the intake, I doubt there are problems with air getting to the motor. The intake manifold clogs up due to a bend in the pipe where the goo collects. I've seen really gummed up intakes, that still had pretty clean intake ports on the head: enough to let it run fine.


Good luck

[jtanguay]

also if your EGR valve is stuck open it will give you some whack idling problems.  

if i were you i would install a block off plate for the EGR but re-install it so it looks stock  :wink: you won't need to clean your intake anymore, and this might stop your idle/low rpm low power issues.

our dodge caravan @ approx 190'000km had a stuck EGR valve.  when cold the motor ran okay because there was extra oxygen in the exhaust stream to help burn the fuel.  when the engine got up to temp, there was little if any oxygen in the exhaust so all that air getting pumped into the engine was basically 'choking' it or starving it of oxygen.  ran like a complete pile of crap and kept stalling etc.  it ran like a charm at highway speeds though, or any time when it was moving.  my dad bought an egr valve for around $200 and installed it himself.  the van ran practically like new!

sounds a little bit like your problem.. especially since you had to clean the intake after only 20'000km... imagine what the EGR valve must look like  :shock: